Improvement in molds for casting



UNITED STATES f PATENT t OFFICE.

MORTIMER NELSON, OF NEW YORK, N. fY.

IMPROVEMENT |N VMotos Fon CASTING.

Specification forming part of Letters Patent No. 17.109, dated April 21, 1857.

To all whom it may concern:

Be it known that I, Moerman NELSON, of

the city, county, and' State of New York, have invented certain-,improvements in thc manufacture of molds for casting britanniaandother metals fusible below a red heat, of which the following isa full, clear, an d exactdescription, reference bein g had to the accompanying drawings, making pairt of this specification, in which- Figures l and 2 are interior views of the two halves ofa mold 'prepared for casting one face of a medal; Fig. 3,:1 section through the same on the line A A.

Difiicultyhas been experienced in reprod ucing in metal, by casting, articles having highlypolished surfaces or iinelines-such as engravin; r or chasing-as'the metallic mold, if made oi'sniicient thickness to obtain the desired strength, would chill the more fusible metal be-v ingT cast in it'before thc delicate lines or parts had been filled; or if the mold were" heated to prevent this the casting would be frosted or often lled with minute holes.

To obviate these objections and to obtain a mold that shall possess sufficient strength and rigidity without containing a mass of metal spi'licient to chill the iluid metal being cast is the object of my present invention, which I will now proceed todcscribe, that ot hers skilled in the artmayunderstand thenianner in which I have carried it out.

lhe said drawin represent a mold taken by my improved process from one side of a medal in the following manner: One halfof the article to be molded is coated with black-lead in the usual way, and a thin sheet of copper is deposited on it by the eleetrotype process. The other half is then treated in the same way, thus forming a perfect mold, even to the nest engraved lines of the articles. These thin sheets B, Fig. 3, are then backed up with plaster-of-paris to the" requisite thickness, as at C, Fig. 3. The copper on its outer surface, being rough, as deposited in the bath, serves to hold two pieces, each portion of it is formed as above described. r

By ,the above process I' obtain a mold having all the advantages ofoneofsolid metal without the disadvantage of chillin g the 1i uid metal when poured intoit, enabling me to' reproduce, in any metal fusing at a less heat than copper, castings having line engraved lilies or devices in a better manner and ata much less cost than has been heretofore practicable. v

W hen the metal employed for casting fuses at a temperature more nearly approaching that of the mold itis liable to adhere to the copper. To prevent this the face of the mold may be brushed over with a thin coating ot' black-lead; or it may be smoked before pouring in the hot metal. For the same purpose the face of the mold may he plated by the ciectrotype process with a thin coat of iron', to

which thc fused metal will not adhere, and which tends to render the mold more durable than when the casting is made upon a surface of copper.

secure by Letters Patent, is

The Within described method of forming molds for casting britannia and other metals by backing up a thin metallic face with plas- What I claim as my invention,'and desire to ter, in the manner substantially as herein set forth.

M. NELSON.

Witnesses: Y

WM. DIXEY, EDWARD BURKE. 

